Sealegs, part of the NZX-listed Future Mobility Systems, manufactures amphibious kits for installation on small boats.
Bryham built and tested initial versions of his designs over a period of years starting from 2000.
Orion Marine was incorporated in 2012 to compete with Sealegs by developing amphibious leg kits for application on medium-sized runabout boats of the same size and type as those using the Sealegs amphibious system.
Its business was established by the fourth defendant, Leybourne, a former employee of Sealegs, and the first defendant Yun Zhang, court papers said.
Shortly afterwards the sixth defendant, Vladan Zubcic, also left his employment at Sealegs and joined Orion Marine.
Sealegs alleged that Orion Marine and the other defendants infringed its copyright interests as the creator of original artistic works as expressed in three specified models of its craft, each of which are equipped with its amphibious retractable leg system.
In the decision, Justice Paul Davison said: "I find that what the defendants did copy was a substantial part of the Sealegs copyright models by reason of their adoption and reproduction of the Sealegs arrangement or pattern of features.
"By doing so they did much more than 'filch' the core design concepts and features embodied in the Sealegs pattern, they unreservedly appropriated it.
"Having first appropriated the Sealegs arrangement or pattern, the independent design work thereafter undertaken by the defendants resulted in some different engineering solutions and a different appearance, but nevertheless retained the essential Sealegs pattern and composition of components," Justice Davison said.
Bryham said the company had sold about 1300 Sealegs units so far, or about 100 a year, and that sales were growing.
FMS has been acquiring assets over the last year or so.
The first acquisition was a 70 per cent interest in Sillinger S.A.S. completed last August.
The company then bought Sealegs Europe SAS in September, giving Sealegs greater control over the sale of Sealegs craft in continental Europe and Africa.
Last October, the FMS bought Lancer Industries, which has a range of own branded products mainly used in marine commercial applications.
In February, FMS bought US-based Willard Marine, which specialises in making small boats for military and commercial use.
For the year to March, FMS reported turnover of $30.3m, an increase of $12.6m or 71 per cent over the previous year.